Lithography techniques include processes in which, for example, a resist film formed from a resist material is formed on top of a substrate, the resist film is selectively irradiated with light or an electron beam or the like through a mask in which a predetermined pattern has been formed, and a developing treatment is then conducted, thereby forming a resist pattern of the prescribed shape in the resist film. Resist materials in which the exposed portions change to become soluble in the developing liquid are term positive materials, whereas resist materials in which the exposed portions change to become insoluble in the developing liquid are termed negative materials.
In recent years, in the production of semiconductor elements and liquid crystal display elements, advances in lithography techniques have lead to rapid progress in the field of pattern miniaturization.
Typically, these miniaturization techniques involve shortening the wavelength of the exposure light source. Conventionally, ultraviolet radiation typified by g-line and i-line radiation has been used. However, recently, mass production of semiconductor elements using KrF excimer lasers and ArF excimer lasers has also commenced. Furthermore, research is also being conducted into radiation with even shorter wavelengths than these excimer lasers, including F2 excimer lasers, electron beams, EUV (extreme ultra violet radiation), and X-rays and the like.
Conventionally, negative resist materials for use in processes that use either i-line radiation or a KrF excimer laser (248 nm) as the light source have employed chemically amplified negative resist compositions containing a combination of an acid generator, an alkali-soluble resin such as a novolak resin or a polyhydroxystyrene, and an amino resin such as a melamine resin or urea resin (for example, see patent reference 1).
Furthermore, negative resist materials that can be applied to processes that use an ArF excimer laser of even shorter wavelength use materials that exhibit improved transparency to ArF excimer lasers. For example, a negative resist composition that includes a resin component containing carboxyl groups, a cross-linker containing alcoholic hydroxyl groups, and an acid generator has been proposed. In this composition, the carboxyl groups within the resin component react with the alcoholic hydroxyl groups of the cross-linker under the action of the acid generated from the acid generator. As a result, the resin component changes from an alkali-soluble state to an alkali-insoluble state.
Furthermore, compositions have also been proposed that include a resin component containing carboxyl groups or carboxylate ester groups as well as alcoholic hydroxyl groups, and an acid generator, wherein an intermolecular reaction between the carboxyl groups or carboxylate ester groups and the alcoholic hydroxyl groups within the resin component, under the action of the acid generated from the acid generator, causes the resin component to change from an alkali-soluble state to an alkali-insoluble state (for example, see non-patent references 1 to 3 and patent reference 2).